Alternating-current motor.



F.'EIOHBERG. ALTERNATING CURRENT MOTOR.

:IAPPLIOATION FILED\APR.19,1907.

Patented 001;.12Q1909. 2 SHEETS-SHEET 1.

' I 'WZTNESSES/ l JJYYEAZTUH I 1 HZEDHZCH K1512 5855 AT TY" F BICHBBRG'. ALTBRNATING CURRENT MOTOR.

I APPLIOATION FILED APB. 19,1907. 7 936,615. Patented Oct. 12, 1909.

2 Bazaarseann: 2.

WITNESSES. INS/ENTER w 3k M. IHEDHEH EIEHBE'H ATTY:

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STATEE ATENT FRIEDRICH EICHBERG, O BERLIN, GERMANY, ASSIGNOB TO GENERAL ELECTRIC- COMIPANY, A CORPGRATION OF NEW YORK.

nnrnnnnrrue-ounnnnr Moron.

Specification of Letters Patent.

Application filed April 19, 1907. Serial No. 369,092.

To all whom it may concern:

Be it known that I, Fmnomorr Eionnnns, a subject of the Emperor of Austria-Hungory, residing at Berlin, Germany, have invented certain new and useful Improve:

4 ments in Alternating--Current Motors, of

which the following is a specification.

My invention relates to alternatingcurrent motors of the type in which the stator is providedwith an inducing winding, and the rotor is short-circuited on the line of magnetization of the inducing winding by means of a commutator and brushes, and the excitation or cross-magnetization o'f-the inotol isproduced by current supplied to the rotor through'brushes displaced 90 olcc trical degrees from the short-oircuiting brushes; and its object is to so arrange such e'motor that. it will operate at constant speed with a high -power-'factor and ciliciency. If a constant voltage is supplied to the exciting brushes or" the rotor, the machine approximates constant speed, but the speed regulation is not close, because of the variation in the electromotive force induced in the rotor winding bet-ween the" exciting brushes due to rotation in the field the nducing 'Wll'lCllIlg and rotor short-circuit.'

This field decreases with increase oi load, because of ohmic drop in the inducting winding, and in the rotor short-circuit, and con sequently the electromotive force induced by this field 'in the rotor winding between the exciting brushes falls 01?. This induced electromotive force opposes the electromotive force of self-induction of the rotor circuit between the exciting brushes, and assists the voltage impressed on these brushes; and consequentiy its reduction decreases the amount of exciting current and also changes its phase in relation to the impressed voltage. Therefore the variation of speed with varying load is quite considerable, and at the same time the power-factor and efficiency are decreased. 7

By my present invenfion I superpose on the shunt excitation produccd by the'constant impressed voltage a series excitation which compensates for the drop in the exciting current.

My invention comprises as one of its features, employing the-rotor winding for the series excitation, as well for the shunt ex citation.

.My inventionwill bastibe understood by short-circuit.

reference to the accompanying drawings, in which Figure 1 shows diagrammatically amot-or arranged in. accordance with my invention, with a series excitation obtained by means of a winding on the stator; F 2 shows a modification in which the series excitation is obtained by means of an auxiliary rotor winding; Fig. 3 shows a further modification, in which the series and shunt excitation are obtained by different portions of the some rotor Winding; Figs. t and 5 show modifications of the arrangement out Fig. 3;

I and Figs. 6 and 7 show modified arrangeand carrying the exciting or cross-magnetizing current. l orthis source l have shown atrz'insfornier C connected across the su1')ply-circuit, a portion of the winding v0t which is connected across the brushes 1) 7). D represents a winding on th stator adapt ed to produce a magnetization of the motor assisting that produced by the current flow ing between the brushes 6 I).

In operation the current flowing in the rotor winding between thebrushes h 7) is determined by the emount of the impressed voltage, the sell iuduction oi the winding.

and the eloctromotive force developed in the 1 rotor winding between these brushes, due

to rotation in theiield of the inducing winding A and the rotor short-circuit. 'll1is induced eleotronfiotire force opposes the elem tromotive force or seltinduction, and assists the in'ipressed x-i'iltagi. As tho load on the motor increases, increasing the currentfimv in the inducing wimling A and the rotor short-circuitbclwoonthe brushes 1) I), the ficldnlong the line of magnetization of tlu winding A, whichiis a transformer field, is reduced in amountbecuusc ot the ohmic drop in the wimhug A and in the rotor (,itfllfietlfllfllil), the oloctromw tive force induced in the rotor wiuiiiug be tween the brushcs l) 1/, duo in rotation in Patented Oct. raises.

to! winding D of Fig. 1. two rotor the exciting Winding D serves for the shunt excitation,

this held, the amount of current flowing through these brushes and the crossonagnetization of the motor produced therebv.

is decreased. thereby 'decreasuiw.

The purpose of is to compensate for this drop in the ihunt excitation. Since this Winding is in series with the inducing winding A, its magnetizing effect is propor tional to thecurrent in winding A, and consequently compensates for shunt excitation.

In Fig 2, 1n pla the drop in the.

ce oi" employing the stawindings one ol which, l3. and the series excitation. Extra supplied for this purpose. windings B or B may be 13 and B. are employed;

other, B, for the brushes 5 b are Either or both' short-circuited on the line. of the inducing winding A. I 4

Fig. 3 shows a modification, in. which ditierent parts of a single rotor winding are employed for producing both the shunt and series excitation. The portion of the transformer L), which in Fig. 1, is connected across brushes 6 7), is, in Fig. connected between the upper'brush Wand the shortcircuited brushes, so that the upper half of the rotor winding alone carries the current for the shunt excitation. The lower brush 1) is connected in series with the inducing winding A, so that the lower half of the rotor winding carries the current for the series excitation.

In Fig. 4 I have shown a further modification, by means of which the relative voltages impressed on theinducing winding A and on the rotor winding for the series excitation may be made anything desired. In this figure a transformer winding D is connected in series with the winding A, and points from this series transformer winding are connected to the lower brush 6 and to the short-circuiting brusl'ies.

It may be noted that the motor maybe caused to start as a series motor by opening either of the leads 2 or 3. For instance, if the lead. 2 opened, the motor starts as a. series motor, with full series excitation,- that is, in Fig. l the current entering the inducing winding A passes through winding 1) and then through the entire rotor winding from the lower brush 6 to the upper brush, so that the entire rotor winding and the winding D assist in producing a strong field. If a weaker field, with less self-induction, is required at starting, by opening lead 3 the motor starts with a series excitation due to the field D alone; the rotor winding bemg idle, as far as producing eross'rnag- .scries transformer D.

ducing winding on the same as that shown in Fig. 4-,with the exception'that the series traustornwr l) is arranged to impress '2. higher voltage on the rotor than exists between the points of con ncction from the transformer to winding A and'to the external circuit.

In place of the arran ement shown in Figs. 1 to 5, inclusive, Ior obtaining the shunt excitation, the arrangement shown in Fig. 6 may be employed. In this figure the shunt excitation is obtained by means of a tap from the inducing windingA, which is connected to the lower brush 5. In this figure the lower half of the armature rves for the shunt excitation; the upper half serving for the series excitation by means of the The switch E is provided for opening the shunt exciting circuit, so as to allow the motor to start as a series motor.

In Fig. '7 the lower half oi. the rotor winding is connected to an auxiliary stator winding a in inductive relation to the main winding A. Thus, the shunt excitationis ob tained from the main winding inductiwly, instead of conductively, as in Fig. In this figure the upper portion of the rotor winding is shown connected directly in series with the inducin winding A, instead of through a transformer, as in Fig. 6.

Other modifications will readily occur to those skilled in the art, and consequently I do not desire to limit myself to the particular construction shown, but aim in the appended claims to cover all modifications which are within the scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is,

l. Ill-H11 alternating-current motor, an instator, a rotor windlng provided with a commutator and brushes short-eircuiting it on the line of magnetizationof the inducing winding,'c0nncctions for impressing a substantially constant voltage on a iartof the rotor winding at points on a line displaced electrical degrees from the line of the short-circuit, and connections for supplying to another part of the rotor winding on the same line a current proportional to the current in the inducing winding.

'2. In an alt'ernatii'igcurrent motor, an inducing winding on the stator, a rotor windin g provided with a commutator and brushes short-circuiting it on the line of tion of the inducing winding, connections for impressing a substantially constant voltage on a part of the rotor winding at points on a line displaced, $30 electrical degrees from the line of the short-circuit, a RTVIi Ji'I in said connections, and cminections for su 'iplying to another part of the rotor finding on the same line current proportional to the can rent in the inducing winding.

lit)

- {mm the short-circuit'ing brushes, connecsecond set and the short-circuiting brushes ducing winding on the stator a rotor wind ing provided with a commutator and brushes short-circuiting it .onthe line of magnetization of the inducing winding, 2. second set of brushes displaced 90 electrical degrees tions for impressing esubstantially constant voltage on the rotor windingebetween one brushof the second set and the short-circuiting brushes, and means for supplying to, the rotor Winding through another brush of the a current proportional to the current in the inducing Winding.

4. In an alternating-current motor, an inducing winding on the stator, a rotor winding provided with a commutator and brushes short-circuiting it on the line of magnetization of the inducing winding, 2 second set of brushes displaced 9O electrical degrees from the short-circuiting brushes, connections for FRIEDRICH Eronnnno.

VVit-nesses JULIUS Rnuumnr,

OSKAR SINGER. 

